Accelerometers are used in various applications, such as measuring the magnitude of an earthquake and gathering seismic data, detecting the magnitude of a collision during a car accident, and detecting the tilting direction and angle of a mobile phone or a game console. As micro-electro-mechanical systems (MEMS) technology continues to progress, nano-scale accelerometers have been widely used in commercial applications.
A gyroscope is able to detect the tilting direction and angle of an object, and has been used in many fields, such as ships and airplanes. As the micro-electro-mechanical systems (MEMS) technology continues to progress, many nano-scale gyroscopes have been widely used in commercial applications, such as automobiles, robots, cellphones, mobile devices, etc.
In contrast to traditional gyroscopes, a MEMS gyroscope does not contain any rotating parts or any bearings. Instead, a MEMS gyroscope uses a vibrating object to sense the angular velocity, and uses vibration to induce and detect the Coriolis force. For example, Chinese Patent Publication No. CN101180516 describes the use of a driver to drive multiple masses in the X direction. When the gyroscope rotates on the Z axis with angular velocity Ω, the mass will induce a Coriolis force Fcori on the Y axis based on the equation listed below, and the gyroscope calculates the angular velocity Ω by measuring the Coriolis force in the Y direction: Fcori=2 mΩv; where m stands for mass, and v stands for velocity.
In order to increase the angular velocity Ω detecting sensitivity, a MEMS gyroscope needs to induce larger Coriolis force during detection. This can be achieved by increasing the mass m of the measurement mass or increasing the driving velocity v of the measurement mass. Most prior patents increase the detecting sensitivity of a gyroscope by increasing the mass m of the measurement mass. For example, Chinese Patent Publication No. CN101135559 increases the overall mass m of the measurement mass by providing multiple measurement masses. During measurement, a larger Coriolis force is generated, thus increasing the sensitivity of the gyroscope. However, providing multiple measurement masses on the same plane increases the chip size. Also, in a multiple-mass system, it is hard to keep the size of each measurement mass uniform. Therefore, energy is lost due to coupling, which decreases the sensitivity and induces noises. Furthermore, the range of motion between two masses is different.
In this disclosure, a solution is provided where two masses are connected with elastic beams to achieve a uniform displacement. However, during the manufacturing process, an offset may be generated to the elastic beam size, which limits the detection sensitivity. A structure having two masses also requires two electrical sensing circuits, which increases the circuit complexity and the energy consumption.